The FBI did demand a separate non-disclosure agreement from agents assigned to the Hillary Clinton e-mail probe, Fox News’ Catherine Herridge reported this morning. Agents had to agree not to discuss the case outside of the investigation, and were told that polygraph tests could well be involved to make sure the cone of silence remained in effect. The Senate Judiciary Committee got word two weeks ago of the unusual arrangements, including an apparent bar on speaking to members of Congress — which chair Sen. Charles Grassley (R-IA) complained was a violation of whistleblower protections:

The FBI has confirmed to a senior Republican senator that agents were sworn to secrecy — and subject to lie detector tests — in the Hillary Clinton email probe, an extensive measure one former agent said could have a “chilling effect.”

A July 1 letter sent by a senior deputy to FBI Director James Comey to Senate Judiciary Committee Chairman Charles Grassley, R-Iowa, detailed the restrictions on agents. The letter, reviewed by Fox News, confirmed agents signed a “Case Briefing Acknowledgement” which says the disclosure of information is “strictly prohibited” without prior approval, and those who sign are subject to lie detector tests.

“The purpose of this form is to maintain an official record of persons knowledgeable of a highly sensitive Federal Bureau of Investigation counterintelligence investigation,” the agreement attached to the Grassley letter reads, “….I (FBI agent) also understand that, due to the nature and sensitivity of this investigation, compliance with these restrictions may be subject to verification by polygraph examination.”

The measures show the extent to which the bureau has gone to keep additional details of the politically sensitive case from going public. While Comey has provided some information ‎on why the FBI did not opt to pursue charges, Attorney General Loretta Lynch repeatedly ducked questions on specifics of the case at a House hearing Tuesday.

FBI investigators already have agreements to keep their work confidential. Why demand the additional NDA? Megyn Kelly discussed a New York Post report from yesterday that said some agents believe that the bureau cut a deal to ensure that no charges would be recommended at the end of the probe, and that the NDAs were a warning not to divulge anything that would make the arrangement obvious:

If that were the case, though, why would James Comey have held a press conference to read his indicting non-indictment aloud to the press? Comey made the case that the FBI found evidence of lawbreaking — in fact, it was so convincing that lawmakers couldn’t understand why Comey didn’t recommend prosecution. If the idea was to frighten investigators into keeping quiet to keep questions from being asked, no one told Comey about it.

There may be a simpler explanation for the requirement. At no other time in the FBI’s post-Hoover history had they been forced by circumstances to conduct a criminal probe of a major-party presidential candidate. The pressure on the FBI has been intense, and the temptation of individual agents to leak details must also have been enormous.

Add that up with the number of agents working on the case, and the potential for disaster looks astronomical. If the probe had started to spring leaks, accusations of politicking from one or all sides of the scandal would have immediately discredited it, and disgraced the FBI. With these extraordinary circumstances, the bureau may simply have decided to put extraordinary controls in place to remind everyone of the stakes involved. It seems to have worked; few substantive leaks emerged.

Let’s say that’s what happened. The need for the extraordinary NDAs has therefore expired. Are agents now free to discuss their findings, or at least as free as they are with other cases (which isn’t very free at all, remember)? Perhaps Judiciary chair Chuck Grassley should invite some of them to discuss it with his panel and find out. There may be some whistleblowers who now feel safe in being heard.